am f8dbf375: am 2c7e6cb7: Merge "docs: add tabs to JB highlights" into jb-mr1-dev

page.title=Jelly Bean Highlights for Developers

page.title=Jelly Bean

@jd:body

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<ul id="version-tabs">

  <li class="selected"><a href="#android-42">Android 4.2</a></li>

  <li><a href="#android-41">Android 4.1</a></li>

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<!-- BEGIN ANDROID 4.2 -->

<div id="android-4.2">

<div id="android-42" class="version-section">

<div style="float:right;padding:0px 0px 12px 34px;">

<div>

<img src="{@docRoot}images/jb-device-2.png" alt="Android 4.2 on phone and tablet" height="348" width="400">

href="http://www.android.com/whatsnew">www.android.com</a>.</p>

<h2 id="4.2-4.2performance">Faster, Smoother, More Responsive</h2>

<h2 id="42-performance">Faster, Smoother, More Responsive</h2>

<p>Android 4.2 builds on the performance improvements already included in Jelly Bean

&mdash; <strong>vsync timing</strong>, <strong>triple buffering</strong>,

<img src="{@docRoot}images/jb-nexus10-1.png" alt="10-inch tablet running Android 4.2" width="380" /></a>

</div> 

<h2 id="4.2-ui" style="margin-top:2em;">Refined, refreshed UI</h2>

<h2 id="42-ui" style="margin-top:2em;">Refined, refreshed UI</h2>

<p>Android 4.2 refines the Jelly Bean user experience and brings familiar

Android UI patterns such as status bar, system bar, and notifications window to

Tray</strong> is also available on all screen sizes.</p>

<h2 id="4.2-multiuser" style="margin-top:2em;clear:left;">One tablet, many users</h2>

<h2 id="42-multiuser" style="margin-top:2em;clear:left;">One tablet, many users</h2>

<p>Now several users can <strong>share a single Android tablet</strong>, with

each user having convenient access to a <strong>dedicated user

environment and there are no changes you need to make in your existing or

published APKs. The system manages your app in each user space just as it does

in a single-user environment. </p>

</div>

<h2 id="4.2-engagement" style="clear:left; margin-top:1em;">New ways to engage users</h2>

<h2 id="42-engagement" style="clear:left; margin-top:1em;">New ways to engage users</h2>

<div style="float:right;margin:22px 0px 0px 24px;width:280px;">

<div>

<p class="image-caption" style="padding:1.5em">You can extend <strong>app widgets</strong> to run on the lock screen, for instant access to your content.</p>

</div>

<h3 id="4.2-lockscreen-widgets">Lock screen widgets</h3>

<h3 id="42-lockscreen-widgets">Lock screen widgets</h3>

<p>In Android 4.2, users can place <strong>app widgets</strong> directly on

their <strong>lock screens</strong>, for instant access to favorite app content

also add features to your widgets that might be especially useful or convenient

on the lock screen.</p>

<h3 id="4.2-daydreams">Daydream</h3>

<h3 id="42-daydreams">Daydream</h3>

<p>Daydream is an <strong>interactive screensaver mode</strong> that starts when

a user’s device is docked or charging. In this mode, the system launches a

app. You can provide multiple daydreams in your app and you can offer distinct

content and display settings for each.</p>

<h2  id="4.2-external-display" style="clear:left;">External display support</h2>

<h2  id="42-external-display" style="clear:left;">External display support</h2>

<p>Android 4.2 introduces platform support for <strong>external

displays</strong> that goes far beyond mirroring &mdash; apps can now target

device. Apps can build on this to deliver new kinds of interaction and

entertainment experiences to users.</p>

<h3 id="4.2-display-manager">Display manager</h3>

<h3 id="42-display-manager">Display manager</h3>

<p>Apps interact with displays through a new display manager system service.

Your app can enumerate the displays and check the capabilities of each,

their capabilities change, to better manage your content on external

displays.</p>

<h3 id="4.2-presentation">Presentation window</h3>

<h3 id="42-presentation">Presentation window</h3>

<p>To make it easy to show content on an external display, the framework

provides a new UI object called a <strong>Presentation</strong> &mdash; a type of dialog that

<p class="image-caption" style="padding:1.25em">You can take full control of two or more independent displays using <strong>Presentation</strong>.</p>

</div>

</div>

<p>A Presentation gives your app full control over the remote display window and

its content and lets you manage it based on user input events such as key

arbitrary view hierarchy to using SurfaceView or SurfaceTexture to draw directly

into the window for streamed content or camera previews.</p>

<h3 id="4.2-preferred display">Preferred display selection</h3>

<h3 id="42-preferred display">Preferred display selection</h3>

<p>When multiple external displays are available, you can create as many

Presentations as you need, with each one showing unique content on a specific

router’s MediaRouteActionProvider and MediaRouteButton to offer standard

display-selection UI.</p>

<h3 id="4.2-protected-content">Protected content</h3>

<h3 id="42-protected-content">Protected content</h3>

<p>For apps that handle protected or encrypted content, the display API now

reports the <strong>secure video capabilities</strong> of attached displays. Your app query a

app can set a secure flag to indicate that the contents should never appear in

screenshots or on a non-secure display output, even when mirrored.</p>

<h3 id="4.2-wireless-display">Wireless display</h3>

<h3 id="42-wireless-display">Wireless display</h3>

<p>Starting in Android 4.2, users on supported devices can connect to an

external display over Wi-Fi, using <a

display as needed.</p>

<h2 id="4.2-native-rtl">Native RTL support</h2>

<h2 id="42-native-rtl">Native RTL support</h2>

<div style="float:right;margin:22px 0px 0px 24px;width:340px;">

<div>

text direction, and text alignment for all the Views in the hierarchy,</p>

<h2 id="4.2-intl">Enhancements for international languages</h2>

<h2 id="42-intl">Enhancements for international languages</h2>

<p>Android 4.2 includes a variety of <strong>font and character

optimizations</strong> for international users:</p>

</ul>

<h2 id="4.2-ui-tools">New ways to create beautiful UI</h2>

<h2 id="42-ui-tools">New ways to create beautiful UI</h2>

<h3 id="4.2-nested-fragments">Nested Fragments</h3>

<h3 id="42-nested-fragments">Nested Fragments</h3>

<p>For more control over your UI components and to make them more modular,

Android 4.2 lets you <strong>nest Fragments inside of Fragments</strong>. For

Library</strong>.</p>

<h2 id="4.2-accessibility">Accessibility</h2>

<h2 id="42-accessibility">Accessibility</h2>

<p>The system now helps accessibility services <strong>distinguish between touch

exploration and accessibility gestures</strong> while in touch-exploration mode.

accessibility services through AccessibilityNodeInfo.</p>

<h2 id="4.2-camera">Improved Camera with HDR</h2>

<h2 id="42-camera">Improved Camera with HDR</h2>

<p>Android 4.2 introduces a <strong>new camera hardware interface and

pipeline</strong> for improved performance. On supported devices, apps can use a

which is recommended.</p>

<h2 id="4.2-renderscript">Renderscript Computation</h2>

<h2 id="42-renderscript">Renderscript Computation</h2>

<p>In Android 4.2, Renderscript Compute introduces new scripting features, new

optimizations, and direct GPU integration for the highest performance in

computation operations.</p>

<h3 id="4.2-filterscript">Filterscript</h3>

<h3 id="42-filterscript">Filterscript</h3>

<p>Filterscript is a subset of Renderscript that is focused on <strong>optimized

image processing across a broad range of device chipsets</strong>. Developers

your operations are optimized and accelerated on more types of device chipsets. 

Any app targeting API level 17 or higher can make use of Filterscript.</p>

<h3 id="4.2-rs-intrinsics">Script intrinsics</h3>

<h3 id="42-rs-intrinsics">Script intrinsics</h3>

<p>In Android 4.2, Renderscript adds support for a set of script intrinsics

&mdash; pre-implemented <strong>filtering primitives that are

<p>Intrinsics are available for blends, blur, color matrix, 3x3  and 5x5 convolve,

per-channel lookup table, and converting an Android YUV buffer to RGB.</p>

<h3 id="4.2-rs-groups">Script groups</h3>

<h3 id="42-rs-groups">Script groups</h3>

<p>You can now create <strong>groups of Renderscript scripts</strong> and

execute them all with a single call as though they were part of a single script.

these operations for best performance.</p>

<h3 id="4.2-rs-optimization">Ongoing optimization improvements</h3>

<h3 id="42-rs-optimization">Ongoing optimization improvements</h3>

<p>When you use Renderscript for computation operations, you apps benefit from

<strong>ongoing performance and optimization improvements</strong> in the

the performance gain delivered by ongoing Renderscript optimization improvements

across successive versions of the Android platform.</p>

<h3 id="4.2-gpu-compute">GPU Compute</h3>

<h3 id="42-gpu-compute">GPU Compute</h3>

<p>Renderscript Compute is the first computation platform ported to run directly on a mobile device GPU. It now

automatically takes advantage of <strong>GPU computation</strong> resources

this GPU integration, without recompiling. The Nexus 10 tablet is the first

device to support this integration.</p>

<h2  id="4.2-dev-options" style="clear:right;margin-top:1em;">New built-in developer options</h2>

<h2  id="42-dev-options" style="clear:right;margin-top:1em;">New built-in developer options</h2>

<p>The Android 4.2 system includes a variety of new developer options that make

it easier to create great looking apps that perform well. The new options expose

execution using Logcat, Systrace, or callstack on glGetError.</li>

</ul>

<h2 id="4.2-platform-tech" style="padding-top:1em;clear:left;">New Platform Technologies</h2>

<h2 id="42-platform-tech" style="padding-top:1em;clear:left;">New Platform Technologies</h2>

<p>Android 4.2 includes a variety of new and <strong>enhanced platform technologies</strong> to

support innovative communications use-cases across a broad range of hardware

devices. In most cases, the new platform technologies and enhancements do not directly

affect your apps, so you can benefit from them without any modification.</p>

<h3 id="4.2-security">Security enhancements</h3>

<h3 id="42-security">Security enhancements</h3>

<p>Every Android release includes dozens of security enhancements to protect

users.  Here are some of the enhancements in Android 4.2:</p>

with earlier versions of Android may also include these fixes.</li>

</ul>

<h3 id="4.2-bt-stack">New Bluetooth stack</h3>

<h3 id="42-bt-stack">New Bluetooth stack</h3>

Android 4.2 introduces a new Bluetooth stack optimized for use with Android

devices. The new Bluetooth stack developed in collaboration between Google and

Broadcom replaces the stack based on BlueZ and provides improved compatibility

and reliability.

<h3 id="4.2-audio">Low-latency audio</h3>

<h3 id="42-audio">Low-latency audio</h3>

<p>Android 4.2 improves support for low-latency audio playback, starting from the

improvements made in Android 4.1 release for audio output latency using OpenSL

AudioManager APIs are provided to query the native audio sample rate and buffer

size, for use on devices which claim this feature.</p>

<h3 id="4.2-camera-interface">New camera hardware interface</h3>

<h3 id="42-camera-interface">New camera hardware interface</h3>

Android 4.2 introduces a new implementation of the camera stack. The camera

subsystem includes the implementations for components in the camera pipeline

such as burst mode capture with processing controls.

<h3 id="4.2-nfc-interface">New NFC hardware interface and controller interface</h3>

<h3 id="42-nfc-interface">New NFC hardware interface and controller interface</h3>

Android 4.2 introduces support for controllers based on the NCI standard from

the NFC-Forum. NCI provides a standard communication protocol between an NFC

Controller (NFCC) and a device Host, and the new NFC stack developed in

collaboration between Google and Broadcom supports it.  

<h3 id="4.2-dalvik">Dalvik runtime optimizations</h3>

<h3 id="42-dalvik">Dalvik runtime optimizations</h3>

<p>The Dalvik runtime includes enhancements for performance and security across

a wider range of architectures:</p>

</div> <!-- END ANDROID 4.2 -->

<!-- BEGIN ANDROID 4.1 -->

<div id="android-4.1">

<div id="android-41" class="version-section">

<div style="float:right;width:320px;padding:0px 0px 0px 34px;clear:both">

<div>

<p>For more information about the APIs included in Google Play Services, see the <a href="http://developers.google.com/android/google-play-services/index.html">Google Play services</a> developer page.</p>

</div> <!-- END ANDROID 4.1 -->